A Review of the Impacts of Off-Road Vehicles on Special Ecosystems

Editor’s Note: This BiblioNote is an excerpt from Wildlands CPR and Wild Utah’s ORV BMPs published in 2008. To see a list of Best Management Practices for planning and management of ORV routes or to view the full report click here.

Certain ecosystems are very rare, or are disproportionately ecologically or socially important. These “special ecosystems” need particular management attention because they are often more sensitive and more susceptible to damage from off-road vehicles (ORVs), or because the degradation of these areas by ORVs is more significant by virtue of their rarity. This section reviews the impacts of ORVs on roadless areas, riparian areas, and other special ecosystems.

Roadless Areas

Many forestlands have no roads and have not been significantly altered by motorized disturbances. These roadless areas maintain healthy soil, provide clean water, and act as a refuge for wildlife (USDA 2000b; DellaSala and Strittholt 2002). Roadless areas have remained unroaded primarily because they are remote and inaccessible. Today, most remote roadless areas can be accessed in just a few hours on an ORV.

ORVs may negatively impact roadless areas by increasing legal and illegal harvest of wildlife, reducing hunter opportunity as seasons become more restrictive, fragmenting wildlife populations, and decreasing overall habitat quality and quantity. ORVs may also impact native fish and plant species by enabling non-native invasive species to travel and be transported deep into roadless areas.

Roadless areas are very important for a variety of wildlife species. Roadless areas allow for landscape and regional connectivity, and can act as refugia for a host of wildlife. For example, one study in Idaho found that 75 percent of all elk harvested in a hunting unit were from roadless areas, which was just 25 percent of the forested portion of this drainage (Thiessen 1976). In Minnesota, researchers found that wolves could persist with higher road densities if there was an adjacent roadless area (Mech 1989). During a 10-year study of grizzly bears, Dood et al. (1983) recorded five of six illegally killed bears in roaded  areas, although their home ranges included roadless areas.

Roadless areas have the potential to conserve sensitive, threatened, or endangered species (Loucks et al. 2003). Forest Service roadless areas are known aquatic strongholds for salmonids and other fish species (Quigley et al. 1997). Additionally, roadless areas are a significant refuge for native plant species (Gelbard and Harrison 2003). Roadless areas also generally have less fire risk and fewer insect outbreaks than heavily logged areas (DellaSala and Frost 2001).

Riparian Areas and Wetlands Riparian areas are the vegetated areas adjacent to streams that are regularly flooded during high flows. Wetlands are areas with saturated soils that support deep rooted, or obligate wetland plants. While riparian areas and wetlands make up just a small percentage of forestlands, they are generally more productive in plant and animal biomass and higher in diversity than the surrounding areas. These areas are also vulnerable to ORV use. ORVs in riparian areas can disturb wildlife, cause bank erosion, and increase stream sedimentation. ORVs in wetlands can cause similar damage to sensitive wetland soils and plants.

Healthy, vegetated riparian areas provide cover, foraging, and nesting sites for a number of animals. In addition to providing habitat for resident populations, riparian areas have been shown to act as important corridors for wildlife (Naiman et al. 1993, Machtans et al. 1996, Burbrink et al. 1998). One study found that riparian areas contained up to 10 times the number of migrant birds per  hectare than adjacent, nonriparian plots (Stevens et al. 1977). Healthy riparian zones and streams are also crucial for fish populations (Stevens et al. 2005 and references within).

Riparian areas also provide a number of ecosystem service functions including capturing, storing, and filtering water. Following a storm or snowmelt, riparian areas hold and store water and slowly release it back to the stream, resulting in healthy and normal hydrographs. Degraded riparian areas typically exhibit more stream flashing. Healthy riparian areas, through bankcover and root masses, also serve to stabilize stream banks. Stable stream banks have been shown to be very important for fish habitat (USDA 1985), water tables near the surface (Richards 1987, Stevens et al. 1995), and most importantly for preventing erosion (Stevens et al. 2005). Trimble (1997) found that up to 76% of total sediment entering creeks may come from creek bank erosion alone. Wetlands provide similarly important ecosystem functions, such as improving water quality by filtering sediments, nutrients and contaminants from the water column (Meffe and Carroll 1994). They are also critically important habitats for an impressive variety of plants and both vertebrate and invertebrate species, including many federally threatened and endangered species.

Other Special Areas

Cliffs are unique features on a landscape that provide security for many nesting raptors. ORVs have the potential to disturb nesting birds when routes are located close to cliffs (Hamann et al. 1999). Caves are an important feature for breeding bats. Human disturbance can cause bats to abandon a roost and lead to population declines (Pierson and Rainey 1994). Caves and old mine tunnels are a lure for a number of forest visitors and recreationists. For many, simply seeing one from a trail is reason enough to explore, and some of those explorers will go on to vandalize the cave or mine. Unfortunately vandalism can sometimes mean purposely disturbing roosting bats, and sometimes even with means that include fireworks, shooting, and fire (pers. comm., George Oliver, Utah Division of Wildlife Resources). Alpine meadows are also sensitive to human disturbance because of their short growing season and slow soil formation (Fitzgerald et al. 1994). Finally, much like other special areas, the increase of ORV use in remote areas is threatening archaeological and historic sites. Increased visitation has resulted in intentional and unintentional damage to many cultural sites (USDI 2000b, Schiffman 2005).

— Adam is Science Coordinator for Wildlands CPR and Allison is Conservation Biologist for the Wild Utah Project.

Literature Cited

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